The tradition mention above has also been transmitted by Abu Musa through a different chain if narrators. But there is no mention of demand of repentance.
Sunan Abi Dawud Book 40, Hadith 7
← Previous Hadith A man who turned back from Islam was brought to Abu Musa. He invited him to repent for twenty days or about so. Muadh then came and invited him (to embrace Islam) but he refused. So he was beheaded.

Sunan Abi Dawud Book 40, Hadith 6 Next Hadith → Abdullah ibn AbuSarh used to write (the revelation) for the Messenger of Allah (ﷺ). Satan made him slip, and he joined the infidels. The Messenger of Allah (ﷺ) commanded to kill him on the day of Conquest (of Mecca). Uthman ibn Affan sought protection for him. The Messenger of Allah (ﷺ) gave him protection.

Sunan Abi Dawud Book 40, Hadith 8